Pretreatment method for chelate resin having pyridine ring used for collecting catalyst in aromatic carboxylic acid production process

ABSTRACT

In pretreating a pyridine ring-containing chelate resin which is used in the step for adsorption and collection of a heavy metal ion and a bromide ion derived from a catalyst from the oxidation reaction mother liquid in the process of producing an aromatic carboxylic acid, there may occur phenomena such as swelling of the resin, heat generation of the resin, and air bubbles generation, thereby causing fracture and deterioration of the resin. As a first treatment, Br −  conversion, under a certain condition, of a pyridine ring-containing chelate resin with an aqueous solution of hydrobromic acid is performed, and then as a second treatment, replacement with acetic acid solvent is performed, thereby making it possible to prevent fracture and deterioration of the resin.

TECHNICAL FIELD

The present invention relates to a pretreatment method of a pyridinering-containing chelate resin, which is used for adsorption andcollection of a heavy metal ion and a bromide ion derived from acatalyst, from the oxidation reaction mother liquid discharged in aprocess of producing an aromatic carboxylic acid.

BACKGROUND ART

An aromatic carboxylic acid is produced through liquid-phase oxidationof an alkyl group-containing aromatic hydrocarbon, in which, in general,used is a catalyst such as cobalt, manganese or the like, or a catalystfurther added with a promoter such as a bromine compound, acetaldehydeor the like, in the presence of an acetic acid solvent.

A slurry containing the aromatic carboxylic acid produced through suchliquid-phase oxidation is, in general, processed for crystallization bylowering the temperature thereof, and then further processed forsolid-liquid separation under a pressure close to ordinary pressure togive an aromatic carboxylic acid cake.

On the other hand, the oxidation reaction mother liquid separatedthrough the solid-liquid separation contains useful catalyst componentssuch as a heavy metal ion, a bromide ion or the like derived from thecatalyst, and in industrial operation, the production cost must bereduced by recycling these catalyst components.

A simplest recycling method includes directly returning the oxidationreaction mother liquid to the reaction system for reusing it therein,and is widely employed in an industrial-scale production process.However, the oxidation reaction mother liquid is contaminated withvarious organic impurities formed as by-products and inorganicimpurities derived from plant corrosion; and it is known that, when theoxidation reaction mother liquid is directly reused in the reactionsystem, then the concentration of these impurities in the reactionsystem may gradually increase, and when the concentration exceeds acertain level, then it would have some negative influences on theliquid-phase oxidation reaction.

For example, in case where the aromatic carboxylic acid is isophthalicacid, it is said that the proportion of the oxidation reaction motherliquid to be returned to the reaction system is generally from 60 to90%, and the remaining oxidation reaction mother liquid of from 10 to40%, which is not reused in the reaction system, is fed to a step ofrecovering the solvent, acetic acid. In case where the aromaticcarboxylic acid is 2,6-naphthalenedicarboxylic acid, it is said that theproportion of the oxidation reaction mother liquid to be returned to thereaction system is generally from 30 to 90%, and the remaining oxidationreaction mother liquid of from 10 to 70%, which is not reused in thereaction system, is fed to a step of recovering the solvent, aceticacid.

As a method for recovering and reusing the catalyst components from theoxidation reaction mother liquid fed to the step of recovering theacetic acid, there has been proposed a method of using a pyridinering-containing chelate resin (see PTL 1).

As described in PTL 1, since the pyridine ring-containing chelate resinis, in general, not used in an ordinary water solvent system but used inan acetic acid solvent system, the chelate resin needs to be replacedwith an acetic acid solvent in advance, and, in addition, since abromide ion exists in a high concentration in the oxidation reactionmother liquid, the chelate resin needs to hold a bromide ion as ananion. The condition where the resin holds a bromide ion is hereinafterreferred to as Br⁻ form.

However, it has become clear that, when a pyridine ring-containingchelate resin containing water as a solvent is brought into contact withan acetic acid solvent, then there occur phenomena unfavorable forpretreatment operation such as the swelling of the resin, heatgeneration of the resin and air bubbles generation.

The swelling of the pyridine ring-containing chelate resin is caused bychange in the solvent-containing condition of the resin resulted fromthe replacement of the water solvent taken inside the resin with theacetic acid solvent. In fact, when a water solvent of a pyridinering-containing chelate resin is replaced with an acetic acid solvent,the resin swells by about 1.7 times based on the packed volume thereof,and in treatment of the pyridine ring-containing chelate resin in anamount to be actually used in an industrial-scale aromatic carboxylicacid production process, attention should be paid to physical fracturingof the resin owing to rapid swelling thereof and to physical fracturingthereof owing to consolidation of the resins together.

Heat generation of the pyridine ring-containing chelate resin in thereplacement of the water solvent with an acetic acid solvent isunexpected, and the details of the reason why the resin could generateheat are unknown. However, for example, it is known that, in replacingthe water solvent of the pyridine ring-containing chelate resin filledin a column with an acetic acid solvent in an up-flow stream, thetemperature of the chelate resin layer rises by about 30° C. dependingon the condition, and such heat generation has some negative influenceson the pyridine ring-containing chelate resin of which the heatresistance is problematic.

Regarding the heat resistance of a pyridine ring-containing chelateresin, a pyridine ring removal test is described in a literature (seePTL 2), in which the resin is added to a solution of 90-mass % aceticacid/10-mass % water kept boiling at a temperature of 110° C., and after140 hours, the nitrogen concentration in the solution is measured todetermine the pyridine ring removal rate from the resin, and it is knownthat the pyridine ring is removed by heat.

Regarding the generation of air bubbles, when a pyridine ring-containingchelate resin is filled in a column, there is an undesirable possibilityof channeling generation and increase in pressure difference in theresin layer owing to the remaining air bubbles.

Regarding literatures relating to a pyridine ring-containing chelateresin, there are a literature relating to a production method for theresin (see PTL 3), a literature relating to a method for selectivelyremoving a metal ion from a solution by the use of the resin (see PTL4), and a literature relating to a method of recovering an oxidationcatalyst by the use of the resin (see PTLs 1 and 5).

Regarding the description relating to swelling and contraction of apyridine ring-containing chelate resin, for example, PTL 6 describes “itis not preferred that the degree of crosslinking is lower than 10%,because when the degree of crosslinking is lower than 10%, the resinstructure may become greatly swollen or contracted by a reaction solventsuch as acetic acid or the like, thereby causing break, deterioration orthe like”. In addition, PTL 7 describes “the resin was formed into aslurry with water in the ion-exchange column. The resin swelled, . . .”. Further, PTL 8 describes “it is considered that, when the value ofthe resin volume expansion rate is more than 20%, the change in thephysical structure of the resin carrier would become great in such adegree that the effect of enhancing the heat-resistant stability and theabrasion resistance of the resin carrier could not be expressed”.However, the descriptions in PTLs 6, 7 and 8 relating to swelling andcontraction of the resin are general matters, and the literatures do notrefer to swelling and contraction of a pyridine ring-containing chelateresin in replacement of the water solvent for the resin with an organicsolvent (methanol, acetic acid, etc.).

On the other hand, PTLs 3 and 5 describe replacement of the watersolvent of a pyridine ring-containing chelate resin with an organicsolvent (methanol, acetic acid, etc.), but have no description at allindicating, as a result of the replacement, swelling of the resin, heatgeneration of the resin or air bubbles generation.

PTL 4 has a description relating to swelling, saying that “the stage ofcontact is carried out by making the solution run through the resinlayer in the up-flow direction to thereby swell the resin bed”, however,this relates to the contact method in removal of a metal ion from thesolution, but does not relate to a pretreatment method of a pyridinering-containing chelate resin.

Further, relating to pretreatment of a pyridine ring-containing chelateresin, PTL 1 has a description as follows: “For brominating a pyridinering-containing chelate resin, for example, but not limited thereto,there is a method of bringing the resin into contact with an aqueoussolution of the above-mentioned bromine compound such as sodium bromide,hydrogen bromide or the like or with a mixed solution of said aqueoussolution with acetic acid, followed by washing it with glacial aceticacid or with water-containing acetic acid having a water concentrationof at most 15% by mass to remove the excessive bromine”. However,neither does the literature disclose the phenomenon of swelling of thepyridine ring-containing chelate resin, heat generation of the resin orair bubbles generation in pretreatment of the resin.

CITATION LIST Patent Literature

PTL 1: WO2008/075572

PTL 2: JP-A 6-315637

PTL 3: JP-A 53-10680

PTL 4: JP-T 2003-527950

PTL 5: JP-A 53-102290

PTL 6: JP-A 5-306253

PTL 7: JP-T 6-506211

PTL 8: JP-A 2002-233763

SUMMARY OF INVENTION Technical Problem

There has not as yet been realized an industrial method capable ofpreventing as much as possible the swelling of the chelate resin, heatgeneration of the chelate resin and air bubbles generation in convertingthe pyridine ring-containing chelate resin containing water as a solventinto a Br” form thereof with acetic acid being a solvent (hereinafterthis may be referred to as “Br⁻ form (acetic acid solvent)”).

Accordingly, an object of the present invention is to solve theabove-mentioned problem and to realize a pretreatment method of apyridine ring-containing resin, which converts a pyridinering-containing resin into a Br⁻ form (acetic acid solvent) thereof withneither fracturing nor deterioration of the resin.

Solution to Problem

The present inventors have made assiduous studies for attaining theabove-mentioned object and, as a result, have found out a stable andsimple pretreatment method and have reached the present invention.Specifically, the present invention includes the following (1) to (12).

(1) A pretreatment method of a pyridine ring-containing chelate resin,

wherein, when the pyridine ring-containing chelate resin used forcollecting a liquid-phase oxidation catalyst in a production process ofan aromatic carboxylic acid is pretreated, the pretreatment method iscapable of preventing volume expansion and heat generation of thepyridine ring-containing chelate resin in converting the pyridinering-containing chelate resin containing water as a solvent into a Br⁻form thereof with acetic acid being a solvent,

the pretreatment method comprising:

first, converting the pyridine ring-containing chelate resin into a Br⁻form thereof by use of an aqueous solution of hydrobromic acid having anHBr content of from 0.05 to 10% by mass and having an acetic acidcontent of from 0 to 30% by mass; and

then, bringing the resulting resin into contact with an acetic acidsolvent.

(2) The pretreatment method of a pyridine ring-containing chelate resinaccording to above (1), wherein

the acetic acid solvent has a water content of from 1 to 50% by mass.

(3) The pretreatment method of a pyridine ring-containing chelate resinaccording to above (1), wherein

the pyridine ring-containing chelate resin before the pretreatment is anOH⁻ form thereof.

(4) The pretreatment method of a pyridine ring-containing chelate resinaccording to above (1), wherein

the volume expansion of the pyridine ring-containing chelate resin fallswithin a range of from 1.00 to 1.40 times and the temperature elevationof the pyridine ring-containing chelate resin falls within a range offrom 0 to 15° C.

(5) The pretreatment method of a pyridine ring-containing chelate resinaccording to above (1), wherein

the amount of the bromide ion adsorbed by converting the pyridinering-containing chelate resin into the Br⁻ form thereof is, per the dryweight of the chelate resin, from 0.10 to 1.60 [g/g-dry resin].

(6) The pretreatment method of a pyridine ring-containing chelate resinaccording to above (1), wherein

the pretreatment method is carried out in a batch mode.

(7) The pretreatment method of a pyridine ring-containing chelate resinaccording to above (1), wherein

in converting the pyridine ring-containing chelate resin into the Br⁻form (acetic acid solvent) thereof, the chelate resin is filled in acolumn, the aqueous solution of hydrobromic acid is continuously fedfrom the bottom of the column in an up-flow stream to thereby bring thesolution into contact with the chelate resin, and then the acetic acidsolvent is continuously fed from the bottom of the column in an up-flowstream to thereby bring the solvent into contact with the chelate resin.

(8) The pretreatment method of a pyridine ring-containing chelate resinaccording to above (7), wherein

the amount of the aqueous solution of hydrobromic acid to be fed fromthe bottom of the column is, as a linear velocity based on an emptycolumn, from 0.5 to 12 [m/hr].

(9) The pretreatment method of a pyridine ring-containing chelate resinaccording to above (7), wherein

the amount of the acetic acid solvent to be fed from the bottom of thecolumn is, as a linear velocity based on an empty column, from 0.5 to 12[m/hr].

(10) The pretreatment method of a pyridine ring-containing chelate resinaccording to above (1), wherein

the temperatures of the aqueous solution of hydrobromic acid and theacetic acid solvent to be used for the pretreatment fall within a rangeof from 10 to 100° C.

(11) The pretreatment method of a pyridine ring-containing chelate resinaccording to above (1), wherein

the aromatic carboxylic acid is isophthalic acid.

(12) The pretreatment method of a pyridine ring-containing chelate resinaccording to above (1), wherein

the aromatic carboxylic acid is 2,6-naphthalenedicarboxylic acid.

Advantageous Effects of Invention

According to the present invention, by performing, first, Br⁻ conversionwith an aqueous solution of hydrobromic acid and then performingreplacement with an acetic acid solvent, the swelling and heatgeneration of the pyridine ring-containing chelate resin and the airbubbles generation are prevented, and consequently, the pretreatment ofconverting the resin into a Br⁻ form (acetic acid solvent) thereof withneither fracturing nor deterioration of the resin can be realized.

DESCRIPTION OF EMBODIMENTS [Aromatic Carboxylic Acid]

The aromatic carboxylic acid to which the present invention is directedis one produced through liquid-phase oxidation of an alkylgroup-containing aromatic hydrocarbon. The alkyl group-containingaromatic hydrocarbon may be any and every compound in which at least onemethyl group is substituted with an aromatic ring, and in which thearomatic ring may be any of an aromatic hydrocarbon ring or an aromatichetero ring.

Specific examples of the alkyl group-containing aromatic hydrocarboninclude toluene, orthoxylene, metaxylene, 1,3,5-trimethylbenzene,1,2,4-trimethylbenzene, 1,2,4,5-tetramethylbenzene,2,4-dimethylbenzaldehyde, 3,4-dimethylbenzaldehyde,2,4,5-trimethylbenzaldehyde, 1,5-dimethylnaphthalene,2,6-dimethylnaphthalene, etc.

Specific examples of the aromatic carboxylic acid include benzoic acid,phthalic acid, isophthalic acid, metatoluic acid, trimesic acid,3,5-dimethylbenzoic acid, trimellitic acid, pyromellitic acid,1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, etc.However, terephthalic acid is excluded.

[Pyridine Ring-Containing Chelate Resin]

The pyridine ring-containing chelate resin for use in the presentinvention is one to be used in recovering the liquid-phase oxidationcatalyst in a production process for an aromatic carboxylic acid, and isa resin having a pyridine ring and obtained through copolymerization ofa 4-vinylpyridine monomer and, as a crosslinking agent, divinylbenzene.The production method for the resin is described in detail in PTL 3.

A chelate resin generally has a ligand coordinating with a metal ion toform a complex, is a polymer substrate insoluble in water, and has thefunction of selectively adsorbing and separating a specific metal ion.Specifically having a pyridine ring, the chelate resin has the advantageof efficiently adsorbing a heavy metal ion.

As such a pyridine ring-containing chelate resin, commercially-availableones may be used here. The commercial products include, for example,“REILLEX® 425Polymer” (trade name by Vertellus), “Sumichelate® CR-2”(trade name by Sumika Chemtex), etc.

The liquid-phase oxidation catalyst to be recovered by the use of theabove-mentioned pyridine ring-containing chelate resin may be any oneusable in a production process for an aromatic carboxylic acid, and, forexample, but not limited thereto, includes heavy metal compounds such ascobalt compounds, manganese compounds or the like, as optionallycombined with any of nickel compounds, cerium compounds, zirconiumcompounds, etc. In addition, also usable here is a catalyst with apromoter, such as a bromine compound, acetaldehyde or the like, addedthereto.

[Pretreatment Method of Pyridine Ring-Containing Chelate Resin]

The pretreatment method of the present invention is a method capable ofpreventing volume expansion and heat generation of a pyridinering-containing chelate resin in converting the pyridine ring-containingchelate resin containing water as a solvent into a Br⁻ form (acetic acidsolvent) thereof, and includes, first, converting the pyridinering-containing chelate resin into a Br⁻ form thereof by use of anaqueous solution of hydrobromic acid having an HBr content of from 0.05to 10% by mass and having an acetic acid content of from 0 to 30% bymass (bromination), and then bringing the resulting resin into contactwith an acetic acid solvent (replacement with acetic acid solvent).

(Bromination)

In case where the pyridine ring-containing chelate resin is an OH⁻ form(water solvent form) thereof, the resin may be directly processed forpretreatment. The OH⁻ form means that the chelate resin is kept holdinga hydroxide ion as the anion, like the Br⁻ form (the same shall apply toCl⁻ form and SO₄ ²⁻ form to be mentioned hereinunder). In case where theresin is a Cl⁻ form or SO₄ ²⁻ form thereof, it is preferable that theresin is washed with an aqueous dilute alkali solution (for example,aqueous 1.5 N-NaOH solution) and then washed with water according to anordinary washing method with an ion-exchange resin to thereby convertthe resin into an OH⁻ form thereof, and then the resulting resin isprocessed for pretreatment according to the present invention. Thewashing may be attained in any method of batch-mode or packedcolumn-mode (in which the liquid is continuously fed from the bottom ofthe column) operation.

In case where the HBr content of the aqueous hydrobromic acid solutionto be used in converting the pyridine ring-containing chelate resin intoa Br⁻ form thereof is high, the amount of the liquid to be brought intocontact with the resin would decrease and uniform contact therebetweenwould be difficult; but when the content is low, a large amount of theliquid would have to be used and the treatment would be difficult. Fromthese viewpoints, the range of the HBr content is from 0.05 to 10% bymass, preferably from 0.05 to 9% by mass, more preferably from 0.05 to5% by mass, even more preferably from 0.05 to 3% by mass.

The aqueous hydrobromic acid solution to be used contains acetic acid inan amount of from 0 to 30% by mass; and from the viewpoint of volumeexpansion, heat generation and air bubbles generation, the acetic acidcontent is preferably from 0 to 25% by mass, more preferably from 0 to20% by mass.

The amount of the bromide ion to be adsorbed by the pyridinering-containing chelate resin is, per the dry weight of the chelateresin, preferably from 0.10 to 1.60 [g/g-dry resin], more preferablyfrom 0.10 to 1.00 [g/g-dry resin]. This is in order that the resin couldsufficiently exhibit the adsorption activity thereof when adsorbingcatalyst-derived heavy metal ions, and when the amount of the bromideion that the resin holds is small, then the heavy metal adsorbingactivity of the resin may lower. On the other hand, when the amount ofthe bromide ion that the resin holds is excessive, then the superfluousbromide ion may separate from the resin in the adsorption and collectionof the heavy metal ions, and there may occur bromide ion loss. Fromthese viewpoints, the amount of the bromide ion to be adsorbed by thepyridine ring-containing chelate resin is, per the dry weight of thechelate resin, more preferably from 0.20 to 0.95 [g/g-dry resin], evenmore preferably from 0.30 to 0.90 [g/g-dry resin].

(Replacement with Acetic Acid Solvent)

The acetic acid solvent to be used in replacement with acetic acid,after the pyridine ring-containing chelate resin has been converted intoa Br⁻ form thereof, is preferably water-containing acetic acid having awater content of from 1 to 50% by mass. This is because the waterconcentration in the acetic acid solvent in which the pyridinering-containing chelate resin is actually used falls within that range;and when the water content is more than 50% by mass, then it isunfavorable because the bromide ion having been adsorbed by the resinwould be partly separated from the resin. Form this viewpoint, the watercontent of the acetic acid solvent is preferably from 1 to 30% by mass,more preferably from 1 to 13% by mass.

(Pretreatment Condition)

In pretreatment of the pyridine ring-containing chelate resin, the resinmay be brought into contact with each of the above-mentioned aqueoushydrobromic acid solution and the acetic acid solvent in any method ofbatch-mode or packed column-mode (in which the liquid is continuouslyfed from the bottom of the column) operation.

The advantage of the batch-mode operation is that the condition of theresin under pretreatment can be monitored, and owing to the stir in acontainer, the resin would be hardly fractured through physical contactbetween them even though the resin has swollen or contracted. Inaddition, the entire resin can be uniformly processed. Since the heatgeneration through the pretreatment could be averaged, its influence onthe resin would be little and air bubbles generation would producelittle problem. However, in order that the pyridine ring-containingchelate resin after the pretreatment (Br⁻ form (acetic acid solvent)) isfilled in a column for final use thereof, a method in which the organicsolvent and the strong acid are not exposed to human bodies orenvironment must be employed, and therefore the operation thereof istroublesome.

The advantage of the packed column-mode operation is that the pyridinering-containing chelate resin containing water as the solvent can befilled in a column and the filling operation can be attained safely andstably. In addition, when the fine powder of the chelate resin isremoved through up-flow stream prior to the pretreatment, the watersolvent can be used with no limitation, and the fine powder removal canbe surely completed.

However, when the suitable condition is not employed in the pretreatmentafter filling in the column, then the resin may swell, generate heat orgenerate air bubbles and may therefore undergo physical fracturing orchemical deterioration, thereby detracting the performance of the resin.

The indication in continuously feeding the aqueous solution ofhydrobromic acid from the bottom of the column in the packed column-modetreatment is that the chelate resin layer filled in the column isfluidized by the up-flow stream occurring therein, and in the fluidizedstate, the physical and chemical influences on the resin may beeliminated. The fluidized state can be realized by controlling thelinear velocity (based on an empty column) of the fed liquid that runsupward in the column, to be preferably from 0.5 to 12 [m/hr], morepreferably from 1 to 8 [m/hr], even more preferably from 2 to 6 [m/hr].

Similarly, the indication in continuously feeding the acetic acidsolvent from the bottom of the column in the packed column-modetreatment is that the chelate resin layer filled in the column isfluidized by the up-flow stream occurring therein, and in the fluidizedstate, the physical and chemical influences on the resin may beeliminated. The fluidized state can be realized by controlling thelinear velocity (based on an empty column) of the fed liquid that runsupward in the column, to be preferably from 0.5 to 12 [m/hr], morepreferably from 1 to 8 [m/hr], even more preferably from 2 to 6 [m/hr].

The temperature of the aqueous solution of hydrobromic acid and theacetic acid solvent to be used for the pretreatment may be set freely inany range not having any influence on the pyridine ring-containingchelate resin. When the temperature is low, the liquid viscosity mayincrease and the resin could be less fluidized; but on the other hand,when the temperature is higher than 100° C., then the pyridine ring inthe resin would be readily released. In consideration of these, thetemperature is preferably within a range of from 10 to 100° C., morepreferably from 15 to 90° C., even more preferably from 20 to 85° C.

According to the present invention, the pyridine ring-containing chelateresin is first converted into a Br⁻ form thereof with the aqueoussolution of hydrobromic acid and then subjected to the replacement withthe acetic acid solvent, whereby the swelling of the pyridinering-containing chelate resin, heat generation and air bubblesgeneration are prevented, and consequently, the resin can be convertedinto a Br⁻ form (acetic acid solvent) thereof through pretreatment withneither fracturing nor deterioration of the resin. As a result, in thepresent invention, the volume expansion of the pyridine ring-containingchelate resin in converting the resin into a Br⁻ form (acetic acidsolvent) thereof can be controlled to fall within a range of preferablyfrom 1.00 to 1.40 times, more preferably from 1.00 to 1.35 times, evenmore preferably from 1.00 to 1.30 times; and in addition, thetemperature elevation owing to the heat generation of the pyridinering-containing chelate resin can be controlled to fall within a rangeof preferably from 0 to 15° C., more preferably from 0 to 12° C., evenmore preferably from 0 to 8° C.

EXAMPLES

The present invention is described in more detail by the followingExamples and others; however, the present invention is not limited atall by these Examples, etc.

In Examples and Comparative Examples, “REILLEX® 425 Polymer” (tradename, by Vertellus) was used as a pyridine ring-containing chelateresin.

The volume expansion rate, the adsorbed bromide ion amount and thebromide ion concentration were determined as follows:

<Volume Expansion Rate>

The volume expansion rate of the pyridine ring-containing chelate resinin pretreatment was determined from the chelate resin layer packedvolume (static state) before and after treatment. When the packed volumebefore treatment is represented by V₁ [m³] and the packed volume aftertreatment is represented by V₂ [m³], then the volume expansion rate isrepresented as follows:

Volume Expansion Rate [times]=V ₂ /V ₁

<Amount of Adsorbed Bromide Ion (Br⁻)>

The amount of the bromide ion adsorbed by the pyridine ring-containingchelate resin by bromination was calculated as follows:

-   Bromide ion supply: M₁ [g]-   Aqueous hydrobromic acid solution supply: X₁ [g]-   HBr content in aqueous hydrobromic acid solution supply: C₁ [%]

M ₁ =X ₁ ×C ₁/100

-   Bromide ion emission: M₂ [g]-   Liquid emission: X₂ [g]-   HBr content in liquid emission: C₂ [%]

M ₂ =X ₂ ×C ₂/100

-   Amount of pyridine ring-containing chelate resin to be pretreated:    R_(W) [g]-   Water content of pyridine ring-containing chelate resin: Y [%]-   Dry resin-based amount of pyridine ring-containing chelate resin:    R_(D) [g]

R _(D) =R _(W)×(100−Y)/100

-   Amount of bromide ion adsorbed by pyridine ring-containing chelate    resin: A [g/g-dry resin]

A=(M ₁ −M ₂)/R _(D)

<Method for Measurement of Bromide Ion Concentration>

The bromide ion concentration was measured using the followingapparatus. Titrator: Potentiometric automatic titrator, AT-510 (by KyotoElectronics Manufacturing Co., Ltd.)

<Water Content of Acetic Acid Solvent>

Measured according to Karl-Fischer moisture titration method.

Example 1 (Resin Filling)

With a water solvent, 3.85 [kg] of REILLEX® 425Polymer was filled in aglass column (inner diameter 100 mm, height 1500 mm, equipped with80-mesh SUS316-made grating at the bottom) from the top opening thereof.Next, a water solvent (temperature 24° C.) was fed from the bottomsupply opening equipped at lower than the grating, at 30 [L/hr] for 2hours with overflowing through the top overflow opening, whereby thefine powder of the resin was removed with the up-flow stream running inthe column. After the operation, the height of the chelate resin layerin a static state was 750 mm.

(First Treatment: Bromination)

An aqueous hydrobromic acid solution having an HBr content of 1.2% bymass (temperature 24° C.) was fed from the bottom supply opening at 30[L/hr] (at a linear velocity of 3.8 [m/hr] based on an empty column) tothereby perform the Br⁻ conversion of the pyridine ring-containingchelate resin in the up-flow stream of the solution. At the time whenthe bromide ion concentration detected in the overflow discharge at thetop overflow opening exceeded 200 ppm, the operation was finished.During the operation, the temperature of the chelate resin layer rose byat most 3° C. From the balance between the bromide ion supply anddischarge, the amount of the bromide ion adsorbed by the chelate resinwas 0.71 [g/g-dry resin]. No air bubbles formed. After the operation,the height of the chelate resin layer in a static state was 900 mm(volume expansion rate, 1.20 times).

(Second Treatment: Replacement with Acetic Acid Solvent)

An acetic acid solvent having a water content of 7.0% by mass(temperature 24° C.) was fed from the bottom supply opening at 30 [L/hr](at a linear velocity of 3.8 [m/hr] based on an empty column) to therebyperform the replacement with acetic acid solvent of the pyridinering-containing chelate resin in the up-flow stream of the acetic acidsolvent. At the time when the water content of the acetic acid solventdetected in the overflow discharge at the top overflow opening reachedat 10% by mass or less, the operation was finished. During theoperation, the temperature of the chelate resin layer rose by at most 5°C. Some but only slight air bubbles formed, which, however, were not onthe level having some influence on the chelate resin layer. After theoperation, the height of the chelate resin layer in a static state was920 mm (volume expansion rate, 1.23 times).

The results are shown in Table 1.

Example 2 (Resin Filling)

In the same manner as in Example 1, the chelate resin was filled in thecolumn. After the operation, the height of the chelate resin layer in astatic state was 750 mm.

(First Treatment: Bromination)

The first treatment was the same as in Example 1.

During the operation, the temperature of the chelate resin layer rose byat most 3° C. From the balance between the bromide ion supply anddischarge, the amount of the bromide ion adsorbed by the chelate resinwas 0.75 [g/g-dry resin]. No air bubbles formed. After the operation,the height of the chelate resin layer in a static state was 900 mm(volume expansion rate, 1.20 times).

(Second Treatment: Replacement with Acetic Acid Solvent)

The second treatment was the same as in Example 1, except that thetemperature of the acetic acid solvent was changed from 24° C. to 58° C.

During the operation, the temperature of the chelate resin layer rose byat most 2° C. No air bubbles formed. After the operation, the height ofthe chelate resin layer in a static state was 925 mm (volume expansionrate, 1.23 times).

The results are shown in Table 1.

Example 3 (Resin Filling)

In the same manner as in Example 1, the chelate resin was filled in thecolumn. After the operation, the height of the chelate resin layer in astatic state was 750 mm.

(First Treatment: Bromination)

An aqueous hydrobromic acid solution having an HBr content of 5.0% bymass (temperature 24° C.) was fed from the bottom supply opening at 30[L/hr] (at a linear velocity of 3.8 [m/hr] based on an empty column) tothereby perform the Br⁻ conversion of the pyridine ring-containingchelate resin in the up-flow stream of the solution. At the time whenthe bromide ion concentration detected in the overflow discharge at thetop overflow opening reached more than 200 ppm, the operation wasfinished. During the operation, the temperature of the chelate resinlayer rose by at most 4° C., but no air bubbles were formed. The heightof the chelate resin layer in a static state was 900 mm (volumeexpansion rate, 1.20 times). From the balance between the bromide ionsupply and discharge, the amount of the bromide ion adsorbed by thechelate resin was 0.98 [g/g-dry resin].

(Second Treatment: Replacement with Acetic Acid Solvent)

The second treatment was the same as in Example 1.

During the operation, the temperature of the chelate resin layer rose byat most 5° C. Some but only slight air bubbles formed, which, however,were not on the level having some influence on the chelate resin layer.After the operation, the height of the chelate resin layer in a staticstate was 920 mm (volume expansion rate, 1.23 times).

The results are shown in Table 1.

Example 4 (Resin Filling)

In the same manner as in Example 1, the chelate resin was filled in thecolumn. After the operation, the height of the chelate resin layer in astatic state was 750 mm.

(First Treatment: Bromination)

An aqueous hydrobromic acid solution having an HBr content of 10% bymass (temperature 24° C.) was fed into the column from the bottom supplyopening at 30 [L/hr] (at a linear velocity of 3.8 [m/hr] based on anempty column) to thereby convert the pyridine ring-containing chelateresin into a Br⁻ form thereof in the up-flow stream of the solution. Atthe time when the bromide ion concentration detected in the overflowdischarge at the top overflow opening exceeded 200 ppm, the operationwas finished. During the operation, the temperature of the chelate resinlayer rose by at most 5° C., but no air bubbles were formed. The heightof the chelate resin layer in a static state was 910 mm (volumeexpansion rate, 1.21 times). From the balance between the bromide ionsupply and discharge, the amount of the bromide ion adsorbed by thechelate resin was 1.53 [g/g-dry resin].

(Second Treatment: Replacement with Acetic Acid Solvent)

The second treatment was the same as in Example 1.

During the operation, the temperature of the chelate resin layer rose byat most 5° C. Some but only slight air bubbles formed, which, however,were not on the level having some influence on the chelate resin layer.After the operation, the height of the chelate resin layer in a staticstate was 930 mm (volume expansion rate, 1.24 times).

During the treatment of replacement with the acetic acid solvent, thebromide ion adsorbed by the chelate resin partly dissolved out, givingan acetic acid waste solution difficult to discard.

The results are shown in Table 1.

Comparative Example 1 (Resin Filling)

In the same manner as in Example 1, the chelate resin was filled in thecolumn. After the operation, the height of the chelate resin layer in astatic state was 750 mm.

(First Treatment: Replacement with Acetic Acid Solvent)

An acetic acid solvent having a water content of 7.0% by mass(temperature 24° C.) was fed from the bottom supply opening at 30 [L/hr](at a linear velocity of 3.8 [m/hr] based on an empty column) to therebyperform the replacement with acetic acid solvent of the pyridinering-containing chelate resin in the up-flow stream of the acetic acidsolvent. At the time when the water content of the acetic acid solventdetected in the overflow discharge at the top overflow opening reachedat10% by mass or less, the operation was finished. During the operation,the temperature of the chelate resin layer rose by at most 30° C., andthe chelate resin was pushed up owing to the generation of air bubblesso that the chelate resin layer was broken. After the operation, the airbubbles were removed, and the height of the chelate resin layer in astatic state was 1250 mm (volume expansion rate, 1.67 times).

(Second Treatment: Bromination)

An acetic acid solvent having an HBr content of 1.2% by mass (watercontent 8.1% by mass) (temperature 24° C.) was fed from the bottomsupply opening at 30 [L/hr] (at a linear velocity of 3.8 [m/hr] based onan empty column) to thereby perform the Br⁻ conversion of the pyridinering-containing chelate resin in the up-flow stream of the solution. Atthe time when the bromide ion concentration detected in the overflowdischarge at the top overflow opening exceeded 200 ppm, the operationwas finished. During the operation, the temperature of the chelate resinlayer rose by at most 7° C. From the balance between the bromide ionsupply and discharge, the amount of the bromide ion adsorbed by thechelate resin was 0.77 [g/g-dry resin]. No air bubbles formed. After theoperation, the height of the chelate resin layer in a static state was940 mm (volume expansion rate, 1.25 times).

The results are shown in Table 1.

Comparative Example 2 (Resin Filling)

In the same manner as in Example 1, the chelate resin was filled in thecolumn. After the operation, the height of the chelate resin layer in astatic state was 750 mm.

(First Treatment: Replacement with Acetic Acid Solvent)

An acetic acid solvent having a water content of 50% by mass(temperature 24° C.) was fed from the bottom supply opening at 30 [L/hr](at a linear velocity of 3.8 [m/hr] based on an empty column) to therebyperform the replacement with acetic acid solvent of the pyridinering-containing chelate resin in the up-flow stream of the acetic acidsolvent. At the time when the water content of the acetic acid solventdetected in the overflow discharge at the top overflow opening reachedat 55% by mass or less, the operation was finished. During theoperation, the temperature of the chelate resin layer rose by at most22° C., and the chelate resin was pushed up owing to the generation ofair bubbles so that the chelate resin layer was broken. After theoperation, the air bubbles were removed, and the height of the chelateresin layer in a static state was 1020 mm (volume expansion rate, 1.36times).

(Second Treatment: Bromination)

The second treatment was the same as in Comparative Example 1.

During the operation, the temperature of the chelate resin layer rose byat most 5° C. From the balance between the bromide ion supply anddischarge, the amount of the bromide ion adsorbed by the chelate resinwas 0.77 [g/g-dry resin]. No air bubbles formed. After the operation,the height of the chelate resin layer in a static state was 930 mm(volume expansion rate, 1.24 times).

The results are shown in Table 1.

Comparative Example 3 (Resin Filling)

In the same manner as in Example 1, the chelate resin was filled in thecolumn. After the operation, the height of the chelate resin layer in astatic state was 750 mm.

(First Treatment: Replacement with Acetic Acid Solvent, and Bromination)

An acetic acid solvent having an HBr content of 1.2% by mass (watercontent 8.1% by mass) (temperature 24° C.) was fed from the bottomsupply opening at 30 [L/hr] (at a linear velocity of 3.8 [m/hr] based onan empty column) to thereby perform the replacement with acetic acidsolvent of and the Br⁻ conversion of the pyridine ring-containingchelate resin in the up-flow stream of the solution. At the time whenthe water content in the acetic acid solvent detected in the overflowdischarge at the top overflow opening reached at 10% by mass or less andwhen the bromide ion concentration detected therein exceeded 200 ppm,the operation was finished. During the operation, the temperature of thechelate resin layer rose by at most 29° C., and the chelate resin waspushed up owing to the generation of air bubbles so that the chelateresin layer was broken. From the balance between the bromide ion supplyand discharge, the amount of the bromide ion adsorbed by the chelateresin was 0.78 [g/g-dry resin]. After the operation, the air bubbleswere removed, and the height of the chelate resin layer in a staticstate was 940 mm (volume expansion rate, 1.25 times).

The results are shown in Table 1.

Comparative Example 4 (Resin Filling)

In the same manner as in Example 1, the chelate resin was filled in thecolumn. After the operation, the height of the chelate resin layer in astatic state was 750 mm.

(First Treatment: Bromination)

An aqueous hydrobromic acid solution having an HBr content of 0.03% bymass (temperature 24° C.) was fed from the bottom supply opening at 30[L/hr] (at a linear velocity of 3.8 [m/hr] based on an empty column) toperform the Br⁻ conversion of the pyridine ring-containing chelate resinin the up-flow stream of the solution. At the time when the bromide ionconcentration detected in the overflow discharge at the top overflowopening exceeded 200 ppm, the operation was finished. During theoperation, the temperature of the chelate resin layer rose by at most 1°C., and no air bubbles formed. After the operation, the air bubbles wereremoved, and the height of the chelate resin layer in a static state was890 mm (volume expansion rate, 1.19 times). From the balance between thebromide ion supply and discharge, the amount of the bromide ion adsorbedby the chelate resin was 0.62 [g/g-dry resin].

The time taken for the bromination was 6 days herein, while that inExample 1 was 4 hours, and a large quantity of wastewater was generatedhere.

(Second Treatment: Replacement with Acetic Acid Solvent)

The second treatment was the same as in Example 1.

During the operation, the temperature of the chelate resin layer rose byat most 5° C. Some but only slight air bubbles formed, which, however,were not on the level having some influence on the chelate resin layer.After the operation, the height of the chelate resin layer in a staticstate was 915 mm (volume expansion rate, 1.22 times).

The results are shown in Table 1.

Example 5 (Resin Filling)

In the same manner as in Example 1, the chelate resin was filled in thecolumn. After the operation, the height of the chelate resin layer in astatic state was 750 mm.

(First Treatment: Bromination)

An aqueous hydrobromic acid solution having an HBr content of 1.2% bymass (acetic acid content 25% by mass) (temperature 24° C.) was fed fromthe bottom supply opening at 30 [L/hr] (at a linear velocity of 3.8[m/hr] based on an empty column) to thereby perform the Br⁻ conversionof the pyridine ring-containing chelate resin in the up-flow stream ofthe solution. At the time when the bromide ion concentration detected inthe overflow discharge at the top overflow opening exceeded 200 ppm, theoperation was finished. During the operation, the temperature of thechelate resin layer rose by at most 12° C. From the balance between thebromide ion supply and discharge, the amount of the bromide ion adsorbedby the chelate resin was 0.74 [g/g-dry resin]. Some but only slight airbubbles formed, which, however, were not on the level having someinfluence on the chelate resin layer. After the operation, the height ofthe chelate resin layer in a static state was 940 mm (volume expansionrate, 1.25 times).

(Second Treatment: Replacement with Acetic Acid Solvent)

The second treatment was the same as in Example 1.

During the operation, the temperature of the chelate resin layer rose byat most 1° C. No air bubbles formed. After the operation, the height ofthe chelate resin layer in a static state was 930 mm (volume expansionrate, 1.24 times).

The results are shown in Table 1.

Comparative Example 5 (Resin Filling)

In the same manner as in Example 1, the chelate resin was filled in thecolumn. After the operation, the height of the chelate resin layer in astatic state was 750 mm.

(First Treatment: Bromination)

An aqueous hydrobromic acid solution having an HBr content of 1.2% bymass (acetic acid content 50% by mass) (temperature 24° C.) was fed fromthe bottom supply opening at 30 [L/hr] (at a linear velocity of 3.8[m/hr] based on an empty column) to thereby perform the Br⁻ conversionof the pyridine ring-containing chelate resin in the up-flow stream ofthe solution. At the time when the bromide ion concentration detected inthe overflow discharge at the top overflow opening exceeded 200 ppm, theoperation was finished. During the operation, the temperature of thechelate resin layer rose by at most 21° C., and the chelate resin waspushed up owing to the generation of air bubbles so that the chelateresin layer was broken. After the operation, the air bubbles wereremoved, and the height of the chelate resin layer in a static state was1000 mm (volume expansion rate, 1.33 times). From the balance betweenthe bromide ion supply and discharge, the amount of the bromide ionadsorbed by the chelate resin was 0.75 [g/g-dry resin].

(Second Treatment: Replacement with Acetic Acid Solvent)

The second treatment was the same as in Example 1.

During the operation, the temperature of the chelate resin layer rose byat most 1° C. No air bubbles formed. After the operation, the height ofthe chelate resin layer in a static state was 935 mm (volume expansionrate, 1.25 times).

The results are shown in Table 1.

TABLE 1 Comparative Comparative Example 1 Example 2 Example 3 Example 4Example 1 Example 2 First Treatment Bromination Bromination BrominationBromination Replacement Replacement with acetic acid with acetic acidsolvent solvent Solution 1.2% HBr 1.2% HBr 5.0% HBr 10% HBr acetic acidwith acetic acid with aqueous aqueous aqueous aqueous 7.0% water 50%water solution solution solution solution content content Temperature [°C.] 24 24 24 24 24 24 Temperature [° C.] 3 3 4 5 30 22 ElevationGeneration of no no no no yes yes Air Bubbles Volume [times] 1.20 1.201.20 1.21 1.67 1.36 Expansion Rate Second Replacement ReplacementReplacement Replacement Bromination Bromination Treatment with aceticwith acetic with acetic with acetic acid solvent acid solvent acidsolvent acid solvent Solution acetic acid acetic acid acetic acid aceticacid 1.2% HBr acetic 1.2% HBr acetic with 7.0% with 7.0% with 7.0% with7.0% acid solution acid solution water content water content watercontent water content with 8.1% water with 8.1% water content contentTemperature [° C.] 24 58 24 24 24 24 Temperature [° C.] 5 2 5 5 7 5Elevation Generation of yes, but only no yes, but only yes, but only nono Air Bubbles slight slight slight Volume [times] 1.23 1.23 1.23 1.241.25 1.24 Expansion Rate Adsorbed Br⁻ [g/g-resin] 0.71 0.75 0.98 1.530.77 0.77 Amount Remarks HBr-containing acetic acid waste solution wasgenerated in second treatment Comparative Comparative ComparativeExample 3 Example 4 Example 5 Example 5 First Treatment Bromination andBromination Bromination Bromination Replacement with acetic acidSolution 1.2% HBr acetic 0.03% HBr 1.2% HBr 1.2% HBr acid solutionaqueous aqueous solution aqueous solution with 8.1% water solution with25% acetic with 50% acetic content acid content acid content Temperature[° C.] 24 24 24 24 Temperature [° C.] 29 1 12 21 Elevation Generation ofyes no yes, but only yes Air Bubbles slight Volume [times] 1.25 1.191.25 1.33 Expansion Rate Second Replacement Replacement Replacement withTreatment with acetic acid with acetic acid acetic acid solvent solventsolvent Solution acetic acid with acetic acid with acetic acid with 7.0%water 7.0% water 7.0% water content content content Temperature [° C.]24 24 24 Temperature [° C.] 5 1 1 Elevation Generation of yes, but onlyno no Air Bubbles slight Volume [times] 1.22 1.24 1.25 Expansion RateAdsorbed Br⁻ [g/g-resin] 0.78 0.62 0.74 0.75 Amount Remarks Brominationtime was long and a large quantity of wastewater was generated.

INDUSTRIAL APPLICABILITY

The present invention relates to a pretreatment method of a pyridinering-containing chelate resin used for adsorption and collection of aheavy metal ion and a bromide ion derived from a catalyst, from theoxidation reaction mother liquid discharged in a process of producing anaromatic carboxylic acid.

According to the present invention, by performing, first, the Br⁻conversion with an aqueous solution of hydrobromic acid and thenperforming the replacement with an acetic acid solvent, the swelling andheat generation of the pyridine ring-containing chelate resin and theair bubbles generation are prevented, and consequently, the pretreatmentof converting the resin into a Br⁻ form (acetic acid solvent) thereofwith neither fracturing nor deterioration of the resin can be realized.

1. A pretreatment method of a pyridine ring-containing chelate resin,wherein, when the pyridine ring-containing chelate resin used forcollecting a liquid-phase oxidation catalyst in a production process ofan aromatic carboxylic acid is pretreated, the pretreatment method iscapable of preventing volume expansion and heat generation of thepyridine ring-containing chelate resin in converting the pyridinering-containing chelate resin containing water as a solvent into a Br⁻form thereof with acetic acid being a solvent, the pretreatment methodcomprising: first, converting the pyridine ring-containing chelate resininto a Br⁻ form thereof by use of an aqueous solution of hydrobromicacid having an HBr content of from 0.05 to 10% by mass and having anacetic acid content of from 0 to 30% by mass; and then, bringing theresulting resin into contact with an acetic acid solvent.
 2. Thepretreatment method of a pyridine ring-containing chelate resinaccording to claim 1, wherein the acetic acid solvent has a watercontent of from 1 to 50% by mass.
 3. The pretreatment method of apyridine ring-containing chelate resin according to claim 1, wherein thepyridine ring-containing chelate resin before the pretreatment is an OH⁻form thereof.
 4. The pretreatment method of a pyridine ring-containingchelate resin according to claim 1, wherein the volume expansion of thepyridine ring-containing chelate resin falls within a range of from 1.00to 1.40 times and the temperature elevation of the pyridinering-containing chelate resin falls within a range of from 0 to 15° C.5. The pretreatment method of a pyridine ring-containing chelate resinaccording to claim 1, wherein the amount of the bromide ion adsorbed byconverting the pyridine ring-containing chelate resin into the Br⁻ formthereof is, per the dry weight of the chelate resin, from 0.10 to 1.60[g/g-dry resin].
 6. The pretreatment method of a pyridinering-containing chelate resin according to claim 1, wherein thepretreatment method is carried out in a batch mode.
 7. The pretreatmentmethod of a pyridine ring-containing chelate resin according to claim 1,wherein in converting the pyridine ring-containing chelate resin intothe Br⁻ form thereof with acetic acid being a solvent, the chelate resinis filled in a column, the aqueous solution of hydrobromic acid iscontinuously fed from the bottom of the column in an up-flow stream tothereby bring the solution into contact with the chelate resin, and thenthe acetic acid solvent is continuously fed from the bottom of thecolumn in an up-flow stream to thereby bring the solvent into contactwith the chelate resin.
 8. The pretreatment method of a pyridinering-containing chelate resin according to claim 7, wherein the amountof the aqueous solution of hydrobromic acid to be fed from the bottom ofthe column is, as a linear velocity based on an empty column, from 0.5to 12 [m/hr].
 9. The pretreatment method of a pyridine ring-containingchelate resin according to claim 7, wherein the amount of the aceticacid solvent to be fed from the bottom of the column is, as a linearvelocity based on an empty column, from 0.5 to 12 [m/hr].
 10. Thepretreatment method of a pyridine ring-containing chelate resinaccording to claim 1, wherein the temperatures of the aqueous solutionof hydrobromic acid and the acetic acid solvent to be used for thepretreatment fall within a range of from 10 to 100° C.
 11. Thepretreatment method of a pyridine ring-containing chelate resinaccording to claim 1, wherein the aromatic carboxylic acid isisophthalic acid.
 12. The pretreatment method of a pyridinering-containing chelate resin according to claim 1, wherein the aromaticcarboxylic acid is 2,6-naphthalenedicarboxylic acid.